Power transmission



Jan. 8, 1946. M. R. Fox

n POIWERTRANSMISSION Filed Feb. 1l, 1942 2 Sheets-Sheet 2 INVNTGR MELTCM R., FGX

BY q n @M z. MM

A TTORNEY Patented Jan. 8, 1946 2,392,471 POWER TRANSMISSION Milton R. Fox, Detroit, Mich., assignor to Vickers Incorporated, Detroit, Mich., a corporation of Michigan 6 Claims.

This invention relates to power transmissions, particularly to those of the type comprising two or more ud pressure energy translating devices, one of which may function as a pump and an other as a iluid motor.

The invention is more particularly concerned with a power transmission system utilizing a single pump and wherein is incorporated an `accumulator for supplying :duid at a rate in excess of the delivery rate oi the pump. Certain :machines, such as die casters, injection molding machines, etc., frequently require a very rapid stroke on the injector cylinder which is in the nature of a momentary peak load most advantageously handled by the use of an accumulator.

it is an object of the present invention to provide an improved control syst/em for a circuit or" system utilizing a pressure switch together with a solenoid=operated, springncenter'ed, open-center valve.

Further objects and advantages oi the present invention will be apparent from the following description, reference being had to the accompanying drawings whereinI a preferred form of the Y present invention is clearly shown.

in the drawings:

'Figure l is a diagrammatic View of a power transmission system incorporating a preferred form of the present invention.

Figures 2, 3, and l are diagrammatic views oi the main control features of the power transmission circuit of Figure l showing difierent opera tions.

in the embodiment of the invention shown in Figure l, the circuit comprises a pump lil adapted to be driven by a suitable prime mover, such as an electric motor i2. Pump l0 withdraws iluid from a tank it through a suction conduit i@ and delivers the same to a delivery conduit it. The latter hasa relief valve 2c of conventional construction for bypassing oil to the tank lil through conduits 22 and 24 whenever a predetermined pressure is exceeded in the delivery conduit i8.

Conduit I8 extends beyond relief valve 28 to a directional, spring-centered, tour-way valve 26. 'I'he latter comprises a main body having annular ports 28, 30, 32, 34 and 88 formed at spaced positions along bore 38. Valve spool 40, arranged Application February 11, 1942, Serial No. 43%,322

it, while ports 2S and 32 are connected to drain conduits 2t and 5d, respectively, which communicate with a conduit Port connects with a conduit 5d which contains a check valve @onu duit 5t extends beyond check valve 5t to a conn duit 5c which communicates with an accumulator @il and with a reversing valve Port of valve it is connected oy a conduit {i5} the valve The latter comprises a main body hayu ing a longitudinal core provided with plun rality of annular ports arranged along its length, the tank ports or which are connected to the conr1 duit while cylinder ports are con. 1 to Vconduits il@ and which lead to the het rod ends, respectively, of a cylinder=andv motor 52. Valve @d is provided with end and it which contain small throttles or Liweli valves which restrict the liquid discharge :Trein the pilot operating;1 chambers and thus slow own the speed of the spool which is slidahly mounted in bore d@ to control communication be= tween the various ports.

The spool 'lc ci valve is arranged to be shifted under the control of a spring-offset, pilot, :tour-way valve o lerated by a solenoid The pressure port of the valve il@ is supplied with oil from the accumulator through a conduit which connects with the conduit 58. The port or" valve il@ communicates with the tarde through conduits and Q53, while the cylinder ports connect by conduits Q@ and to the pilot I Y operating chambers ot the valve d2.

. after disclosed, to take place. Pressure switch 93 iS. ftt'rnncttrd with the tank conduit 88 which A supply designated L2. Switch ltd also connects conductors il@ and H62 when in its normal position,v illustrated, of which itil leads from L1 through pressure switch @di and of which H2 leads to the solenoid tl and to the other side of the power supply designated L2. The initial energizing circuit of the solenoi et is controlled by a normally-open, momentarycontact, push-button, starting switch l lf3 connected by conductor il@ with solenoid e2, and by conductor Hit with switch tilt.

ln operation, with the parts in the position shown in Figure l, the device is in its rest position, the full delivery passing through -delivery conduit i8, through valved, as hereinbefore disclosed, and through conduit 2d to the tank it.

The pump is thus eectively bypassed, and no uidisdelivered beyond valve 2t.

en lt is desired to start the device, the start switch il@ may be closed to condition the circuit for a rapid traverse forward, as shown in Figure 2. This energizes solenoid 32 through conductors it@ and liti, thereby shifting the spool of the valve t@ downward and admitting the releasing of the starting switch lle, and energize solenoid d2 of valve 26. Ilhis will also deenergize solenoid ed by breaking the connection between the conductors H2 and Sie, if not previously so deenergized by the pressure switch te. The deenergization'of solenoid 82 of valve d will .cause the spool therein to be lifted upward toestablish a connection between conduits all and 9@ to thereby admit pilot pressure uld to the righthand end of the valve S2. The spool l@ therein is accordingly shifted to the' left, connecting cylinder conduit l@ with pressure conduit td and cylinder conduit et with tank conduit 52.

Energization of the solenoid i2 shifts the spool :it of the valve 2t to the right, connecting conduits it and tl to thereby admit pressure iiuid from the pump l@ to the rod end of the motor l2, returning the 'piston therein to the starting l Y as herein disclosed constitutes a preferred form,

pilot pressure oil from the accumulator conduit d8 to the pilot conduit @E where it iiows to the lefthand end of the reversing valve 62. The spool 'Ll-8 of valve e2 is accordingly shifted to the right, establishing a connection between conduits 5S and t8 to therebf,y admit pressure oil from the itis to be understood that other forms might be adopted, all coming within the scope of the claims which follow.

What is claimed is as follows:

l. In a hydraulic power transmission system the combination of a constantly running pump, an elastically loaded accumulator, a huid motor to be operated on a. rapid /stroke at a'greater rate of accumulator t@ to .the head end of the motor l2.

fis the accumulator supplies a large amount of uid under high pressure, the piston in motor l2 is advanced rapidly, the oil discharged from the rod end being returned to thetank through conduits le, 52 and dit. The piston in motor l2 will continue. to advance until the pressure in -the accumulator conduit 58 drops below the'value of the setting of the pressure'switch Sie. rI 'his will cause piston it@ therein to move upwardly, closing electric contact iti which will, through conductors il@ and H2, energize the solenoid ed of valve 2t. The spool d@ therein will be shifted to the. left, establishing a connection between conduits it and 5d to thereby admit pressure iiuid into conduit til, as illustrated in Figure Si.v IThis will direct the-full pump delivery Ato the motor l2 to supplement the accumulator supply, and, upon completing the work, stroke, to recharge the accumue "lator B53. The latter will beso charged until pressure inV conduit E8 rises above the predetermined value. which -wii1 actuate pressure switch 93, causing it to break its aforesaid connection,

deenergizing solenoid di. This'will cause spool d@ of valve 2G to return to its centered position, y

illustrated in' Figure i, to again bypass the pump delivery to` the tank in a manner hereinbefore disclosed.

When the above operations have taken place and to eect -a return stroke, return switch 06 is depressed. llio-accordingly condition the circuit,

as shown in Figure d. This will deenergize solenoid 82. if not previously so deenergizedby iluid displacement than the pump can deliver, a control valve connected between the accumulator and the motor for applying uuid from the accumulator to the motor, a second valve and connections selectively operable to direct the pump delivery either to the accumulator, to the motor directly or to exhaust, electric actuating means for the second valve,.and a pressure -switchre- -sponsive toV a predetermined decrease in accumulator pressure for controlling said actuating means to thereby connect the pump delivery to the accumulator. 4 v

2. In a hydraulic power transsion system the combination of a constantly running pump, an elastically loaded accumulator, a uid motor-to be operated on a rapid stroke at a greater rate of iiuid displacement than the pump can deliver,

, a directional control valve connected'between the accumulator and the motor for selectively applying iiuid from the accumulator to the motor 'for actuation thereof in one direction or applying uid from the pump directly for actuation thereof in the opposite direction, a second valve and connections selectively operable to direct the pump delivery either to the accumulator, to the motor directly or to exhaust, electric actuating n means for the second valve, and a pressure switch responsive to a predetermined decrease in accumulator pressure for controlling said actuating to be operated on a rapid stroke at a greater rate of fluid displacement than the pump can delivery a directional control valve connected between the accumulator and the motor for selectively applyv Y transmission system in the opposite direction, a second valve and connections selectively operable-to direct the pump delivery either to the accumulator, to the motor directly or to exhaust, electric actuating means for the second valve, a pressure switch responsive to a predetermined decrease in accumulator pressure for controlling said actuating means to thereby connect the pump delivery to the accumulator,- and additional switch means for disabling the pressure switch while the pump ls supplying fluid to the motor directly.

4. A combined accumulator-supplied and direct pump-supplied hydraulic system having but a single pump comprising an open-center, springcentered, solenoid-controlled, four-way valve, connections for directing pump delivery from one port of'the four-way valve to icm with the accumulator delivery and for directing the pump delivery alone from another port of the fourway valve, and a pressure switch responsive to accumlator pressure and connected to control the tour-way valve to direct pump delivery to the accumulator in response to a predetermined fall in Pressure therein.

5. A combined accumulator-supplied and direct Pumpsupplied hydraulic system having but a slnsle pump comprising an open-center. springcentered, solenoid-eontrolled, four-way valve,

n multor.

connections for directing Dump delivery from one port of the four-way valve to loin with the accumulator delivery and for directing the pump delivery alone from another port or the four-way valve, a pressure switch responsive to accumulator pressure and connected to control the four-way valve to -direct pump delivery to the accumulator in response to a predetermined fall in pressure therein, additional switch 'means connected to control the four-way valve to direct pump delivery from said other port. and means for disabling the pressure switch in response to actuation of said additional switch. A

6. In a hydraulic power transmission system the combination oi a constantly running pump, an elastically loaded accumulator, a uld motor to be operated on va rapid stroke at a greater rate of iluid displacement than the pump can deliver, a control valve connected between the accumulator andthe motor tor directing iiuid from the accumulator to the motor for actuation thereof in one direction, a second valve and connections selectively operable to direct the pump delivery either to the accumulator, to the motor directly or to exhaust, electric actuating means for the second valve, and a pressure switch responsive to a predetermined decrease in accumulator pressure for controlling said actuating means to thereby connect the pump delivery to the accu- IIILTON R. FOX. 

